3 tablespoons vegetable shortening, melted and cooled
1 recipe lemon filling, below
Preheat the oven to 350 degrees Fahrenheit. Coat an 8-inch round cake pan with cooking spray, or grease it and dust it with flour. Place a parchment paper round in the bottom of the pan.
Crack the eggs into a doubler boiler or heatproof bowl and whisk them thoroughly. Add the sugar and lemon zest. Set the double boiler over a pot of boiling water and whisk the ingredients until the mixture is warm, 3 to 5 minutes. Take the double boiler off the heat and continue beating the mixture with a whisk or electric mixer until it stiffens and cools, a further 5 to 10 minutes.
In a separate bowl, sift the flour with the baking powder and salt. Gradually beat the dry ingredients into the wet mixture.
Add the vegetable shortening to the batter and stir gently with a spatula until fully incorporated.
Place the batter into the prepared cake pan and bake the cake for 20 to 25 minutes or until it passes the toothpick test.
Let the cake cool completely before filling it.
Lemon Filling Recipe
4 egg yolks
1 egg white
1/4 cup vegetable shortening
Juice and zest of 2 lemons
3/4 cup sugar
1/4 teaspoon salt
Place the egg yolks and egg white in a double boiler or heatproof bowl. Beat them with a whisk and set the mixture over a pot of simmering water.
Add the shortening, lemon juice, lemon zest, sugar, and salt to the beaten eggs. Whisk the mixture constantly until it is warm and thickened and the sugar has dissolved completely, about 5 to 10 minutes. Remove the mixture from the heat.
Pour the filling into a bowl and top it with a layer of plastic wrap to prevent it from developing a skin.
Chill the filling for at least 4 hours or overnight.
When ready to use, slice the cake in half horizontally and distribute the lemon filling in the middle. Top the cake with powdered sugar, whipped cream, or your favorite frosting.